Earth compactor



April 12, 1949. H. c. POLLITZ EARTH GOMPACTOR 4 Sheets-Sheet 1 Filed June 23, 1945 fizz E1723? Harold CPOZZIJZE} April 12, 1949. H, c, POLUTZ 2,466,822

EARTH COMPACTOR Filed June 23, 1945 v f 4 Sheets-Sheet 2 April 12, 1949. H. c. POLLITZ EARTH COMPACTOR 4 sheets-sheet 5 Filed June 25, 1945 April 12, 1949. H. c. POLLlTZ EARTH COMPACI OR- 4 Sheets-Sheet Filed June 23, 1945 I Har' Za C'PoZZzZZ- I Patented Apr. 12, 1949 EARTH COMPACTOR Harold C. Pollitz, Cedar Rapids, Iowa, assignor to Iowa Manufacturing Company, Cedar Rapids, Iowa, a corporation of Iowa Application June 23, 1945, Serial No. 601,110

4 Claims. 1

The present invention relates to a method and apparatus for compacting roads, particularly airplane runways, so as to considerably increase their bearing capacity and eliminate cracking thereof such as caused by vibratory pounding by airplane wheels during landing and vibrating forces from engines and heavy loads.

As a result of the present trend of greatly increased sizes of bombing planes and commercial airliners, enormously increased loads have been imposed on runways thus making modern rolling methods and roller equipment unsuitable for compacting the runways to satisfactorily increase their bearing capacity. Attempts have been made to solve this problem by devising various means for increasing the weight of the rollers used for compacting, such as by filling hollow cylindrical roller drums with water and wet sand, or by devising a cart-like roller so that heavy weights such as steel billets, rails or other readily available heavy materials, may be conveniently loaded on the cart as ballast and thereby increase the gross weight of the roller. Roller weights as much as 170,000 lbs. have been attained in this manner. With such heavy loads the frame must be made especially strong and the wheels of the rollers, if pneumatic, must be made of very special and heavy construction, (say about 24 x 82 in. and 36 ply). Furthermore, the handling of such weights requires large labor crews. In spite of large increases in roller weights it has been found that a rather large number of passes (of the order of more than 100 .passes in some cases) are generally required to cause sufiicient compacting of airstrip subgrades to increase their bearing capacity by a sufiicient amount. Furthermore the limit of thickness that can be satisfactorily compacted at one time has generally been about six inches. Attempts have been made to decrease the number of passes by using a roller of the sheepsfoot type, that is, one with a plurality (generally over 100) of projections or sheepsfeet projecting radially outwardly from the roller surface for aiding in compaction of the soil. As the result of progressive compaction the roller eventually climbs out until the sheepsfeet penetrate only a relatively small depth (a few inches) and thereafter a different roller, such as one of the pneumatic type, can be used to finish the operation.

I have found that the outstanding problem of said compaction, namely that of effectively filling voids and spaces in the road material, may best be solved by causing the roller to be vibrated, thereby considerably decreasing the required roll- 2 1er weight to effect a given amount of compacion.

An analogy may be made between soil and a sack of sugar or other granular material. After such sack is filled or packed it may be juggled to cause further settling or packing of the particles. If the sack is poked with a heavy bar it will very likely become punctured. On the other hand, if

the sack is tamped with a light stick the particles will settle. Such settling results because forced vibrations reduce the friction and cohesion between the particles, allowing the particles to move relative to each other and slide into hollow spaces or voids and making the volume less porous, that is, more dense.

Assume now that a weighted roller is being rolled along the surface of a particular soil. Considering a column of this soil extending vertically downwardly from the roller, it will be observed that the cohesion existing between such column and the surrounding sub-surface soil tends to prevent settling down or downward dis placement of the column. However, whentheroller is effectively vibrated so as to cause vibration of the column, the cohesive force between the column and surrounding soil is overcome and the column will thus settle downwardly. The surrounding sub-surface soil tends to keep the column from collapsing as the result of vibration of the weighted roller. Thus, if the roller is of substantial weight and is vibrated excessively, the column may actually buckle or collapse due to insufficiency of the support from the surrounding soil. On the other hand, by vibrating a light roller at too low a frequency, very little or perhaps no appreciable settling will be obtained.

Therefore, for each type of soil or road material, there is an optimum range of weight of the roller and vibration frequency of the roller to obtain appreciable settling of the soil or material. For instance, for a 25 ton tamper with a flat base area of 7.5 square meters the optimum range of vibrations is between 13 and 16 vibrations per second. For a roller such as disclosed herein vibrations of the order of 900 per minute are common. For a given soil there is a particular value of cohesion between the particles as well as a particular value of friction between the particles tending to resist settling. For loose soils the cohesion and friction are very low, hence considerable settling may be obtained by continued vibration. On the other hand in certain soils that are compressed, that have heavy particles, and that have high friction between the particles, alarge portion of the energy developed by the vibrating roller is absorbed by friction between the particles and as the result, Very little settling occurs. Hence, the vibrating roller is most useful for tamping or compacting soils in which the cohesion and inner friction of the particles and weight of the individual particles are relatively low. Of course for loose soils, a large degree of compactionis obtainedzby; tamping fora long period of time until thesoil'becomes extremely dense, on the other hand for dense soils having a large amount of friction between particles, effective tamping can be accomplished only for a relatively short period because the particles soon become so compacted thatfurther tamping is ineffective.

An object of the present invention is to provide a relatively simple and inexpensive method and apparatus for compacting roads, such as airplane runways, so as to considerably increase their bearing capacityand greatly decrease the number of passes necessary for satisfactorycompaction.

A further object of the present invention is to provide improved apparatus for compacting roadways that eliminates the necessity of cumbersome and extremely heavy rollers as generally required in theart.

A more specific object of the present invention is-to provide improvedrapparatus for vibratory pounding of a road, such as anairplane runway, so as to quickly fill up voids and spaces therein and compact the road-Ymaterialso as to makeit withstand heavy bearing loads and vibrations such as caused by landing of airplanes.

A still more specific object ofthe presentinvention is to provide improved roller equipped with a vibrating mechanism for causing substantial vertical vibration of the roller-so that the combined weight and vibration of the roller against the runway (or roadway) will quickly fill voidsand spaces in the roadbed and compactit sufficiently to withstand heavy loads and cracking due to-explosions or pounding by'heavy objects.

The novel features which I'believe to be characteristic ofmy invention are set-forth with particularity in the appended claims. My invention itself, however, both as to its organization, method of operation and manner of construction,

together with further objects and advantages" thereoflmay best be understood byreference .to the accompanying drawings, in which:

Figure 1 is a top view of .a tractor drawing a trailer or roller which roller embodies a vibrating mechanisminaccordance withthe teachings of my invention;

Figure 2 is a side or elevational view of the device shown in Figure 1;

Figure 3 is a rear view. of the:device shown in Figures 1 and 2;

Figure 4 is an enlarged topor planviewof the trailer portion shown in Figures :1 and 2;

Figure 5 is a side orelevational view, partly in cross-section, of the trailer shown in Figures 1 ,a-

and 2;

Figure ,6 is a view, partlyrin cross-section, and with parts broken away of a portion of the trailer taken substantially along line VI'VI of Figure 5;

Figure 7 is an enlarged, sectional viewtaken along line VIIVII of FiguretZ; and

Figure 8 is a schematic diagram of the vi- .brating vmechanism mounted -on the trailer "or roller showing a pair of unbalanced shafts or eccentrics in four difierentpositionstogetherwith members '9 and I0.

source.

vectors showing the directions of the forces and their components.

Referring more particularly to the drawings, especially Figures 1 and 2, numeral I designates, somewhat schematically, a tractor of the crawler type, for example, which drags or pulls a trailer 2, which trailer serves asa weighted roller. The exile 3 of the trailer has 'rotatably mounted at each end thereof through suitable anti-friction means, such as roller bearings 4 (see Figure 6), a pair of dual-wheels 5 and 6 having pneumatic :tires thereon. As shown more clearly in Figure 5, axle 3 has bolted thereon, by suitable fastening means-1, leaf springs 8 and 8a. The ends of springs 8 may be fastened by suitable anti-friction bearings with full shackles to spring mounting It should be noted, however, that other resilient mounting means, such as, for example, coil springs such as used in passenger cars, may be substituted for the leaf springs 8 and 8a. Such coil-spring mounting is-a preferred embodiment in many uses of'the device. Mounting 'members 9 and .10 are secured to a frame 'H which, by means-of springs '8 and 8a,,is resiliently or -,floatingly mounted on the axle. A pair .of counter weights or inertia weights l2 and ['3 are fastened by suitablebolts, such .as M and i5,to

,end portions of the frame! I. Weights l2 and I3 may be of any suitable mass depending upon the particular use for which the device is tobe employed. For examplaeach of the weightsmay be in the neighborhoodof 10,000 ,pounds. Thus, it will be seen that the weights l2 and'i.3,.are floating or resiliently mounted with respect to the axle'3. A plurality of, radiusrodslflandifl are provided having their. .ends pivoted to portions rigidly secured to the-axle and to-the frame 1 I, respectively, so as .to restrict themovementoof weights l2 and. i3 in substantiallythe planeuof Figures ,2 and 5,0f the drawing and insubstantially an up and down direction. .A1arge,-gooseneck pullin g ,tonguell is rigidly secured tothe frame or chassis l I and has-secured thereon ,a

horizontal. swivel connection 22 to compensate for turning of thetractor at a short radius.

A vibrating unit or device I6 of any suitable construction, such asone havingone or more rotating, eccentrically mounted weights, is rigidly secured to axle ,3 by means of mounting; plates fastened to the :axle by mounting bolts 1|). {Ihe vibratingunit may be of any desired construction so long as it effects an upanddownrmove- -ment ofthe axle --3 andwheels towards'and-away from the road surface. Inthe event that one, .or a pair ofrotating eccentrics are used, these-may be driven by means of a-flexible, coupling, such :as

a beltid which is ,drivenybyra motor 25 preferably of variable speed. :For instance,-motor-'25 maybe-a D. Cnmotor.energized-bvmeans of -a 'D. :0. generator 26, :which generator is rigidly mountedson the-reap ofathe tractord and driven which mass or Weight exerts a continuous gravitational force on the wheels in a downward directicn at all times. Since the vibrating unit is rigidly secured to the axle, its efficiency is not impaired by the resistance to vibration such as might otherwise be caused by the heavy weights. While the up and down movement of the axle and frame caused by the vibrating unit is small, the pressure exerted thereby can be varied through rather wide and positive limits. Thus, it will be seen that a relatively heavy weight exerts a continuous gravitational force upon the road surface, which is supplemented by compacting vibrations or impulses in an up and down direction on the axle alternately adding and subtracting from the gravitational force or load but without mutual conflict, and, in this manner, applying to the surface upon which the roller wheels rest the kind of motion that will impart a maximum amount of compaction.

It will be noted that the main movement will be a substantially vertical vibratory movement caused by the vibrating unit IE to be described in detail hereinafter, causing periodic, vibratory pounding of the road surface by the trailer as it is being drawn thereover while its wheels are in continuous contact with the surface to cause compaction by elimination of voids in the roadway material.

The details of vibrating unit iii are best shown in Figure '7.

One of the novel features of the present invention is the provision of a vibrating mechafor applying vertical vibrating forces to the roller or trailer '2. One requisite of a good vibrating mechanism is that the vibrating forces must all act in a single plane, while any other forces or component of forces must neutralize themselves about this plane. A second requisite of a good vibrating mechanism is that all of the vibrating forces must act in a plane passing through the center of gravity of the floating mass which is to be vibrated.

In Figure 7 of the drawings, I have shown such a vibrating mechanism l6 which includes a pair of eccentrically mounted shafts 42 and 43. The machined eccentric end portions 420. and 43a of the shafts 42 and 43, respectively, are mounted in barrel roller bearings 4'! and 48, which, in turn, are carried in end castings 49 and M, respectively. Gears 44- and 45 are mounted on and keyed to the ends of the shafts s2 and t3 and are so arranged that the shaft 42 is rotated in the opposite direction from the shaft 53 and at the same speed. An intermediate housing or cover member '51 extends around the shafts 42 and t3 and is mounted on the end castings 39 and 5! by means of angle members 5% which are bolted or otherwise suitably secured to the housings 49 and 58. The end plates 52 and 53 are also bolted or otherwise suitably secured to the housings 49 and 5! The end plate or hell 53 is provided with a plurality of circular flanges 5 which interengage with like flanges on a bushing 55 to form labyrinth packing to prevent lubricant from escaping from the housing. A complete housing is thus provided for the vibrating mechanism which includes the intermediate housing member 51, the end housings 49 and 5 l, and the end plates 52 and 53. The vibrating mechanism is driven through a drive pulley 58, which is keyed to a reduced extension 43?) of the shaft 43, and this pulley and the bushing 56 are secured in place by means of a nut 59.

Since the shafts 42 and 43 are supported on an axis displaced from their centerline, it is obvious that they provide a mass eccentrically mounted for rotation. They further provide an eccentrically mounted mass which is distributed evenly along the entire length of the shaft rather than being concentrated at one or more spaced points on the shaft. This distributed loading of the shaft enables the use of the material forming the eccentric load to be used for strength, as well as to provide a vibrating force. It will also be appreciated by those skilled in the art that because the vibrating mechanism is completely encased in a housing unit which substantially prevents the infiltration of dust and other foreign matter into the rotating mechanism, that the life of the vibrating mechanism is greatly increased.

It is to be further understood that with this vibrating mechanism, the eccentrically mounted shafts 42 and 43 are symmetrical about a plane perpendicular to a line passing through the supporting axes of the shafts 42 and 43 and intersecting such a line half way therebetween. The shafts 42 and M are rotated in opposite directions and at the same speed, and for that reason all components of unbalanced forces lying in a plane perpendicular to the line of the supporting axes of the two shafts 42 and 43 are cumulative, while all components of unbalanced forces at right angles to this plane are completely balanced out or neutralized.

Figure 8 is a schematic illustration of the unbalanced shaft pair in four different positions, the first position showing the directions of force (represented by arrows) cumulative in a vertically upward direction tending to cause lifting of the trailer; the second position an intermediate position showing a smaller vertically upward force and in which the horizontal components cancel; the third showing no resultant force and complete cancellation of the horizontal components; and the fourth showing cumulative vertically downward forces tending to cause lowering of the trailer, the horizontal components of force canceling;

Therefore, the vibrating unit effects a vertical substantial vibratory movement of the axle and wheels of trailer 2 at somewhat high speed with little interference from the resiliently mounted weights causing the entire weight of the trailer frame to be vibrated at short time intervals of constant value through the resilient cushioning effect of tires 5 and 6 against the surface of the road or runway over which it is drawn and biased by the gravitational force of the floating weight, thereby causing the filling of void spaces in the road material and compacting of the material so as to make it able to withstand heavy bearing loads or shocks.

With the above described vibrating mechanism large depths of the subsoil are compacted at one time by the filling of the voids therein as the result of vertical vibration or cushioned pounding. Whereas heretofore a six inch layer of material has been commonly regarded as the maximum that can be compacted at one time, with the present device, depths as much as 10 feet in sandy soil can be successfully compacted. At a field Where the natural soil forming the subgrade is a plastic clay or adobe, a considerable depth of the subgrade can be compacted in place by using the presently described vibrating method.

Furthermore, by the use of a vibrating mechanism according to the present invention, it is not necessary to make such large numbers of trips by the roller before the runway is satisiace torlly compacted, thus the compacting operation is greatly expedited. By increasing the bearing capacity of the natural subgrade of an airstrip it is possible to so materially decrease the thick? ness of imported fill so as to notably speed up the time of construction and decrease the cost.

Thus, it will be seen that 1 have provided an eficient device for speedily compacting roadways, such as airplane runways, which device is not heavy, unwieldy and cumbersome as devices com? monly used for the purpose, but which is relatively light, simple to manufacture, inexpensive, and requiring a minimum amount of maintenance.

While a vibrating mechanism of a specific type has been described to illustrate the principles of the invention, it will be understood that other vibrating mechanisms may be used instead, so long as the effect is to cause substantial vertical vibration of the roller to efiect compaction of the roadway at a predetermined frequency backed by substantially the entire weight of the trailer or roller.

While I have shown a particular embodiment of my invention, it will, of course, be understood that I do not wish to be limited thereto, since many modifications may be made, and I, therefore, contemplate by the appended claims to cover all such modifications as fall within the true spirit and scope of my invention.

I claim as my invention:

1. A soil compacting apparatus to be drawn over the earth to compact the soil thereon including a member supported by wheels, pneumatic tires on said wheels, a frame having an inertia weight of substantial mass thereon and resiliently mounted on said member for exerting a gravitational force thereon, a vibrator rigidly supported on said member, and a motor rigidly secured to said frame and resiliently coupled to said vibrator to operate said vibrator and cause vibration of said member and wheels toward and away from the surface of said soil substantially independently of said Weight.

'2. A machine for compacting soil as it is moved thereover, comprisin in combination; an axle, wheels supporting said axle, a pneumatic tire on each of said wheels, a weight, resilient means supporting said weight on said axle, and mechanism mounted on said axle to impart vertical vibratory forces thereto, said mechanism comprising a pair of like eccentric members mounted for rotation about parallel horizontal axes, a

drive mechanism mounted on said machine, and connecting means between said drive mechanism and said eccentric members to rotate the same in opposite directions at the same speed.

3. A machine for compacting soil as it is moved thereover comprising in combination; an axle, wheels supporting said axle, a pneumatic tire on each of said wheels, a weight, resilient means supporting said weight on said axle, vertical vibration=producing mechanism, a support mount, ing said vibration mechanism on said axle thereby to impart vertical vibratory forces to said axle, said vibration mechanism comprising a pair of like eccentric members mounted for rotation about substantially parallel horizontal axes, and a drive mechanism mounted on said machine, connecting means between said drive mechanism and said eccentric members to rotate the same in opposite directions at the same speed, and a pair of vertically spaced arms each pivotally connected to said vibration mechanism support and said weight to orient said vibration mechanism to impart force in a substantially vertical direction.

4. A machine for compacting soil as it is moved thereover comprisin in combination; an axle, wheels supporting said axle, a pneumatic tire on each of said wheels, a pair of weights, resilient means supporting said weights on said axle and on opposite sides thereof, said weights being of substantially equal mass and supported at substantially equal distance on each side of said axle, mechanism mounted on said axle to impart vertical vibratory forces thereto, said mechanism comprising a pair of like eccentric members mounted for rotation about substantially parallel horizontal axes, a drive mechanism mounted on said machine, and connecting means between said drive mechanism and said eccentric members to rotate the same in opposite directions at the same speed.

HAROLD C. POLLITZ.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,364,604 Ashmore Jan. 4, 1921 1,733,198 Mullen Oct. 29, 19 9 1,955,101 Sloan Apr. 17, 1934 2,018,294 Baily Oct. 22, 1935 2,110,413 Baily Mar. 8, 1938 2,199,649 Poulter May '7, 1940 2,223,024 Beierlein Nov. 26, 1940 2,224,506 Baily Dec. 10, 1940 2,248,478 Mall July 8, 1941 2,249,264 Baily July 15, 1941 2,287,723 Boyd June 23, 1942 

